To piggy-back a little on Rob's comment:
"In more than one case within RFC-3261, the ABNF does not fully
limit how parsing should occur."
This is a question of semantics versus syntax. The ABNF specifies a
syntax, the requirement that only one tag param be included is a
semantic (not a syntactic) requirement.
It is the same as a c-language requirement that prevents a function such
as:
void func()
{
int *p;
char *p;
}
The C language doesn't allow the same variable name for the two
variables, but the syntax of the above function is correct. Only the
semantics is wrong. The ABNF for C doesn't address this coding error
(and it can't).
-Paul
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Rob
Phillips
Sent: Thursday, October 30, 2003 1:07 PM
To: Srivastava, Samir; Alexandre Charest;
[EMAIL PROTECTED]
Subject: RE: [Sip-implementors] ABNF tag-param in FROM/TO
> I know the accompanying text. I am trying to fix the ABNF by
> restricting the given parameter-name to occur once.
>
> I don't see problem you mentioned in my proposal.
>
> to-additional-param = ( 0*1(SEMI tag-param)) / ( *(SEMI
> generic-param))
> This doesn't forces the tag-param to be the Ist parameter. It says the
> to-additional-param nonterminal can have either tag-param or
> generic-param
Actually, the biggest problem with your ABNF is that it specifies you
can have a tag-param OR any number of generic-params, but not both a
tag-param AND generic-params.
ABNF is not perfect for describing cases like this one, where the order
of parameters is optional but the number of parameters of a particular
type is not. Hence the extra textual information in the specification.
In more than one case within RFC-3261, the ABNF does not fully limit how
parsing should occur. Given that, I think just leaving the ABNF and
accompaning text alone as it is today will be adequate. The implementor
is responsible for understanding both the ABNF and it's context.
- rob
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
